This invention relates to a method and apparatus for detecting metal failures in general and more particularly to an improved method and apparatus of this type which permits making measurements of defects having a transverse component in situ.
Various electronic methods and apparatus for detecting metal failures have been developed. One known type induces eddy currents in the metal and includes means for determining the effect on those currents caused by cracks or other faults in the metal. Such a method, however, cannot reliably detect transverse defects. A second commonly used type is an acoustic type. Although, in many applications these types of measurements are adequate, there are certain areas where their use entails considerable expense.
An example of the problem which exists is the measurement of cracks in nuclear reactors. Quite recently twenty such reactors had to be shut down in order to carry out inspection of the piping in their emergency core cooling systems. Shut down was required since the present method being used, an ultrasonic method, requires that the reactors be shut down cooled and the insulation removed before the measuring equipment can be attached. Needless to say, such a shut down which can last a number of days entails great expense and results in a loss of the electric energy which would normally be generated by these reactors, thereby requiring other generating equipment to make up the loss or brown-outs in the community served.
There are other areas in which detection of faults in piping systems is of extreme importance. For example, six people were recently killed from H.sub.2 S leakage from a pipe failure in a pectro-chemical plant.
From these two examples, it becomes evident there is a need for monitoring and detection equipment for defects having a transverse component which can operate in situ, without requiring a system shut down to avoid the occurrence of accidents and to avoid economic losses associated with shut downs for periodic inspection.